Two Furnace Problems

My Winchester furnace is about 5 years old. Recently, the thermostat stopped kicking the furnace on until you messed with it. Then it would work for an hour or two and stop again. So, I replaced the old dial-type tstat with a brand new digital tstat.

It worked great at first. Then about 2 weeks later it started acting the same way. My grandfather had an extra tstat, just like my new one that he bought for a spare (used lightly, very lightly). It, again, fixed the problem for about 2 days.

While this is going on, at 6am this morning, my blower stops kicking on in auto mode (the furnace is working). My initial thought was, "great! now the blower motor is out!" But, I switched it to manual and it works just fine.

Two Furnace Problems

Sorry,

That's the problem. Okay, having the two separate problems going on at once is confusing. When the furnace doesn't kick on the thermostat does not click. But when the the thermostat clicks, the furnace does kick on. Its like the thermostat doesn't know its supposed to turn on the furnace. (3 thermostats in a row; previously worked fine for 2+years).

Then, when the furnace does kick on, the blower doesn't kick on, the furnace ignites and runs for a while before it overheats and shuts itself off. Turning the fan to manual on resolves that problem and heats the house, but it is now only working in auto mode for a few cycles before quitting again. It is now working part of the time, but not all the time.